Re: HP9000+LVM+Online

Mike, < I won't even try to quote any of your long and informative message!> This is all very useful stuff. *At last* someone is addressing it properly! Is there any way you could make the HP document on RAID available to us here? It is interesting to hear that they own up to RAID's inherent unsuitability for a raw-disk based RDBMS. The only bit I will quote you on is: > Some dbspaces, like the physical and logical logs, have so much > activity on them it is more than one physical disk can cope > with and it is impossible to split these spaces over multiple > disks by conventional means. Have you tried giving the *logical* logs a drive to themselves (or at least shared with data with very light activity)? ie. put the physical logs somewhere else? In the 6.00 OnLine manual that's what Informix are now recommending for an update-thrashed system. If the log backup is in contention with the logical log writes I suppose you could always put alternate logical logs on different drives. What I'm getting to is that tbtape and the log write process will each be doing physically sequential i/o, for the most part one log apart. If you're running them flat out, giving each a drive will all but eliminate head movement. Perhaps that's going a bit far but if you *did* do it you'd have trouble trying to manage it accurately by using LVM as the tool rather than the Online utilities. No, I'm sorry, I still remain unconvinced that LVM offers anything that OnLine's utilities and architecture don't and from your comments on LVM's reliability I'd say it should be given a very wide berth indeed. As for disk mirroring, OnLine 6.00-on also alternates its reads from mirrored drives. The only thing it doesn't seem to do is take into account which drive is less busy. akent@cix.compulink.co.uk (Andy Kent) -------------------------------------